The macro- and microstructures of triple-layered rabbit chondrocyte sheets after vitrification. A-E: Morphological appearance of chondrocyte sheets after vitrification and rewarming. A1-E2: Scanning electron microscopic images of the surfaces of cell sheets recovered after vitrification and rewarming. A1-E1: ×300, Scale bar = 50 μm; A2-E2: ×2,000, Scale bar = 10 μm. The surfaces (A1-E2) are irregular, featuring pavement-like cell populations (arrowheads in A1-E1 indicate representative three cells) and well-developed extracellular matrices with a dense fibrous structure (*). The microstructures of cell sheets vitrified by any of the methods described in this report were similar to those of the non-vitrified control sample.